Semiconductor structure and manufacturing method for the semiconductor structure

ABSTRACT

Embodiments of the present application disclose a semiconductor structure and a manufacturing method for the semiconductor structure, which solve problems of complicated manufacturing process and poor stability and reliability of existing semiconductor structures. The semiconductor structure includes: a substrate; a channel layer and a barrier layer sequentially superimposed on the substrate, wherein the channel layer and the barrier layer are made of GaN-based materials and an upper surface of the barrier layer is Ga-face; and a p-type GaN-based semiconductor layer formed in a gate region of the barrier layer. An upper surface of the p-type GaN-based semiconductor layer is N-face.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/CN2019/079741 filed on Mar. 26, 2019, which is incorporatedherein in its entirety by reference.

TECHNICAL FIELD

The present application relates to the field of microelectronicstechnologies, in particular to a semiconductor structure and amanufacturing method for the semiconductor structure.

BACKGROUND

A High Electron Mobility Transistor (HEMT) is a heterostructure fieldeffect transistor. Taking an AlGaN/GaN heterostructure as an example,due to a strong two-dimensional electron gas in AlGaN/GaNheterostructure, an AlGaN/GaN HEMTs is usually a depletion-mode device,which makes an enhancement-mode device difficult to achieve. In manyrespects, applications of depletion-mode devices have certainlimitations. For example, in the application of power switching devices,enhancement-mode (normally-off) switching devices are required.Enhancement-mode GaN switching devices are mainly used in high-frequencydevices, power switching devices and digital circuits, etc., andresearch for it is of great significance.

In order to realize an enhancement-mode GaN switching device, it isnecessary to find a suitable method to reduce concentration of carriersin a channel under a gate when the gate voltage is zero, for example, amethod of disposing a p-type semiconductor material in a gate region.However, the inventor found that this method has at least the followingdefects:

Disposing a p-type semiconductor material in the gate region requiresselective etching of p-type semiconductors in other regions other thanthe gate region, and precise process control of an etching thickness inan epitaxial direction is very difficult. It is very easy to overetchthe p-type semiconductor and etch semiconductor materials below it, andthe defects caused by the etching may cause serious current collapseeffect, and affect the stability and reliability of the device.

SUMMARY

In view of this, the present application provides a semiconductorstructure and a manufacturing method for the semiconductor structure,which solves problems of complicated manufacturing process and poorstability and reliability of existing semiconductor structures.

The present application provides a manufacturing method for asemiconductor structure, which includes: a substrate; a channel layerand a barrier layer sequentially superimposed on the substrate, whereinthe channel layer and the barrier layer are made of GaN-based materialsand an upper surface of the barrier layer is Ga-face; and a p-typeGaN-based semiconductor layer formed in a gate region of the barrierlayer. An upper surface of the p-type GaN-based semiconductor layer isN-face.

The GaN-based materials described in embodiments of the presentapplication refer to semiconductor materials based on Ga element and Nelement, such as materials of AlGaN, AlInGaN, GaN, etc.

In an embodiment, the channel layer may be made of GaN, and the barrierlayer may be made of AlGaN.

In an embodiment, the semiconductor structure further includes: a gateelectrode disposed on the p-type GaN-based semiconductor layer; a sourceelectrode disposed in a source region of the barrier layer; and a drainelectrode disposed in a drain region of the barrier layer.

In an embodiment, the semiconductor structure further includes: anucleation layer between the channel layer and the substrate; and abuffer layer between the nucleation layer and the channel layer.

In an embodiment, the p-type GaN-based semiconductor layer includes amultilayer structure or a superlattice structure including one or morematerials of p-type AlGaN, p-type GaN, and p-type InGaN.

In an embodiment, the semiconductor structure further includes a groovedisposed in the gate region of the barrier layer, wherein the groovepenetrates the barrier layer and stops on the channel layer or partiallypenetrates the barrier layer and stops in the barrier layer.

The present application provides a manufacturing method for asemiconductor structure, which includes following steps:

preparing a channel layer and a barrier layer sequentially superimposedon a substrate, wherein the channel layer and the barrier layer are madeof GaN-based materials and an upper surface of the barrier layer isGa-face; and

preparing a p-type GaN-based semiconductor layer of GaN-based materialwith N-face as an upper surface above the barrier layer.

In an embodiment, the preparing a p-type GaN-based semiconductor layerof GaN-based material with N-face as an upper surface above the barrierlayer, includes: preparing a p-type Ga-face GaN-based material above thebarrier layer, and doping a polarity reversal element in the p-typeGa-face GaN-based material to reverse the p-type Ga-face GaN-basedmaterial to the p-type GaN-based semiconductor layer of GaN-basedmaterial with N-face as an upper surface.

In an embodiment, the polarity reversal element includes Mg.

In an embodiment, the preparing a p-type GaN-based semiconductor layerof GaN-based material with N-face as an upper surface above the barrierlayer, includes: preparing a p-type Ga-face GaN-based material above thebarrier layer; and reversing the p-type Ga-face GaN-based material by apolarity reversal layer to the p-type GaN-based semiconductor layer ofGaN-based material with N-face as an upper surface.

In an embodiment, the preparing a p-type GaN-based semiconductor layerof GaN-based material with N-face as an upper surface above the barrierlayer, includes: bonding the p-type GaN-based semiconductor layer withN-face as an upper surface to the barrier layer directly.

In an embodiment, the manufacturing method for a semiconductor structurefurther includes: etching the p-type GaN-based semiconductor layerselectively, and reserving only a portion of the p-type GaN-basedsemiconductor layer corresponding to a gate region.

In an embodiment, the manufacturing method for a semiconductor structurefurther includes: preparing a gate electrode on the p-type Ga-basedsemiconductor layer, preparing a source electrode in a source region ofthe barrier layer, and preparing a drain electrode in a drain region ofthe barrier layer.

In an embodiment, the manufacturing method for a semiconductor structurefurther includes: forming a nucleation layer and a buffer layer on thesubstrate sequentially before forming the channel layer.

In an embodiment, before the preparing a p-type GaN-based semiconductorlayer with an N-face as an upper surface above the barrier layer, themanufacturing method for a semiconductor structure further includes:preparing a groove in a gate region of the barrier layer, wherein thegroove penetrates the barrier layer and stops on the channel layer orpartially penetrates the barrier layer and stops in the barrier layer.

According to a semiconductor structure and a manufacturing method forthe semiconductor structure provided by the embodiments of the presentapplication, a p-type GaN-based semiconductor layer is formed in a gateregion on a barrier layer to achieve a purpose of pinching off an n-typeconductive layer under a gate, thereby realizing the semiconductorstructure. More importantly, because an N-face p-type GaN-based materialhas a characteristic of easy corrosion, an etching process is easy tocontrol, a process difficulty of selective etching of the p-typesemiconductor material in the gate region is reduced, and the stabilityand the reliability of a device are improved simultaneously. In the gateregion, a high quality schottky gate may be achieved by using differentmetals and adjusting a work function. In addition, it is also possibleto achieve Mg doping with high doping concentration on a surface ofN-face p-type GaN of the gate, thereby achieving ohmic contact.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 a , 2, 3 a, 3 b, 4 a, 4 b, 4 c, 5 a, 5 b, 6 a, 6 b, 6 c, 6 d and6 e are decomposition schematic diagrams illustrating a semiconductorstructure in preparation processes respectively according to anembodiment of the present application.

FIG. 1 b is a schematic diagram of an atomic structure of Ga-face GaN,and FIG. 1 c is a schematic diagram of an atomic structure of N-faceGaN.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technical schemes of the present application will be described indetail below in combination with specific embodiments shown in theaccompanying drawings. However, it cannot consider that theseembodiments constitute a limitation to the scope of the presentapplication. It should be noted that, and all these structural, method,or functional changes made by those of ordinary skill in the artaccording to these embodiments fall into the protection scope of thepresent application.

In addition, repeated reference numbers or labels may be used indifferent embodiments. These repetitions are only to briefly and clearlydescribe the present application, and do not represent any correlationbetween the different embodiments and/or structures discussed.

A manufacturing method for a semiconductor structure according to anembodiment of the present application includes following steps.

Step 601: as shown in FIG. 1 a , preparing a channel layer 23 and abarrier layer 24 sequentially superimposed on a substrate 1. The barrierlayer 24 is made of a GaN-based material and an upper surface (a surfaceaway from the substrate) of the barrier layer 24 is Ga-face.

In an embodiment of the present application, the channel layer 23 mayalso be made of a GaN-based material, and further, it may also be madeof a Ga-face GaN material.

The GaN-based materials described in the embodiments of the presentapplication refer to semiconductor materials based on Ga element and Nelement, such as materials of AlGaN, AlInGaN, GaN, etc.

The channel layer 23 and the barrier layer 24 may preferably be preparedby a process of Metal-Organic Chemical Vapor Deposition (MOCVD). Ofcourse, this present application is not limited to this. They may alsobe prepared by Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy(HVPE), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD),Chemical Vapor Deposition (CVD) and other preparation methods.

FIG. 1 b is a schematic diagram of an atomic structure of Ga-face GaN,and FIG. 1 c is a schematic diagram of an atomic structure of N-faceGaN. Regarding Ga-face GaN, taking a Ga—N bond parallel to a C axis as areference, Ga atoms in each Ga—N bond are closer to the substrate 1,which is Ga-face GaN. Conversely, taking a Ga—N bond parallel to a Caxis as a reference, if N atoms in each Ga—N bond are closer to thesubstrate 1, it is N-face GaN. For a same GaN-based semiconductor layer,N-face GaN is obtained by reversing the Ga-face GaN in FIG. 1 b . A sidefar from the substrate shown in FIG. 1 b is defined as Ga-face, the sidefar from the substrate shown in FIG. 1 c is defined as N-face, and theGa-face corresponds to the N-face. Since Ga-face GaN and N-face GaN havedifferent atomic arrangements on a side of themselves away from thesubstrate, their characteristics are also different.

The channel layer 23 and barrier layer 24 mentioned above are preparedon the substrate 1. The substrate 1 may be selected from semiconductormaterials, ceramic materials, or polymer materials. For example, thesubstrate 1 is preferably selected from sapphire, diamond, siliconcarbide, silicon, lithium niobate, Silicon on Insulator (SOI), galliumnitride, or aluminum nitride.

The channel layer 23 and the barrier layer 24 may be made ofsemiconductor materials that can form a two-dimensional electron gas.For example, the channel layer 23 may be made of GaN, the barrier layer24 may be made of AlGaN, and the channel layer 23 and the barrier layer24 form a heterostructure to form a two-dimensional electron gas.

In an embodiment of the present application, as shown in FIG. 2 , inorder to improve device performances and meet related technicalrequirements, the semiconductor structure may further include anucleation layer 21 and a buffer layer 22 provided between the substrate1 and the channel layer 23. Taking a GaN-based semiconductor structureas an example, in order to meet technical requirements such as reducingdislocation density and defect density, and improving crystal quality, anucleation layer 21 prepared above the substrate 1 may be furtherincluded. The nucleation layer 21 may be made of one or more materialsof AlN, AlGaN and GaN. In addition, in order to buffer a stress in anepitaxial structure above the substrate and prevent the epitaxialstructure from cracking, the GaN-based semiconductor structure mayfurther include a buffer layer 22 prepared above the nucleation layer21. The buffer layer 22 may be made of one or more of GaN, AlGaN, andAlInGaN. The present application does not specifically limit thearrangements of the nucleation layer 21 and the buffer layer 22.

In this embodiment, only the upper surface (the surface away from thesubstrate) of the barrier layer 24 is defined as the Ga-face, that is,the whole of the barrier layer 24 may be a Ga-face GaN-based material,or only an upper part of the barrier layer 24 away from the substrate isa Ga-face GaN-based material. In another embodiment, the channel layer23 may be further defined as a Ga-face GaN-based material.

Step 602: as shown in FIG. 3 a , preparing a p-type GaN-basedsemiconductor layer 5 above the barrier layer 24, an upper surface ofthe p-type GaN-based semiconductor layer 5 being N-face.

In the above step, preparing the p-type GaN-based semiconductor layer 5with N-face as an upper surface above the barrier layer 24 may beimplemented by various methods.

In an embodiment, during preparing the p-type GaN-based semiconductorlayer 5 of GaN-based material with N-face as an upper surface on thebarrier layer 24, a p-type Ga-face GaN-based material may be epitaxiallygrown first, and a polarity reversal element can be added at the sametime as the epitaxial growth. The polarity reversal element may be, forexample, Mg, etc., so that the Ga-face GaN-based material may become theN-face GaN-based material. Furthermore, when the barrier layer 24 andthe p-type GaN-based semiconductor layer 5 are prepared, they may beepitaxially grown continuously. After the Ga-face barrier layer 24 isprepared, the GaN-based material may be reversed from the Ga-face to theN-face by adding the polarity reversal element. In this embodiment, aprocess of changing the Ga-face to the N-face by adding a polarityreversal element may include a transition process, so a lower surface ofthe p-type GaN-based semiconductor layer 5 close to the barrier layer 24may be the Ga-face. However, a thickness of the Ga-face GaN contained inthe p-type GaN-based semiconductor layer 5 does not exceed 120 nm,preferably it may be controlled below 40 nm, and even more preferably itmay be less than 15 nm. When a lower surface of the p-type GaN-basedsemiconductor layer 5 close to the barrier layer 24 is a Ga-face, aremaining Ga-face GaN that is not etched away may not have a significantimpact on the overall performance of the device due to its thinthickness.

In an embodiment, the p-type GaN-based semiconductor layer 5 with N-faceas an upper surface is prepared on the barrier layer 24, as shown inFIG. 3 b , and during the epitaxial growth process, a polarity reversallayer 31 is prepared on the Ga-face barrier layer 24 to achieve polarityreversal, thereby achieving the preparation of the N-face p-typeGaN-based semiconductor layer 5. Specifically, when the barrier layer 24and the p-type GaN-based semiconductor layer 5 are prepared, they may beepitaxially grown continuously. After the Ga-face barrier layer 24 isprepared, the polarity reversal layer 31 can be prepared, so that theGaN-based material may be reversed from the Ga-face to the N-face. Inthis embodiment, a lower surface of the p-type GaN-based semiconductorlayer 5 close to the barrier layer may also be N-face. For example, thepolarity reversal layer 31 may be Al₂O₃. In addition, when the polarityreversal layer 31 is Al₂O₃, it may also prevent etching, and when thep-type GaN-based semiconductor layer 5 is etched, the etching may bestopped on the polarity reversal layer 31.

In an embodiment, the preparing the p-type GaN-based semiconductor layer5 of GaN-based material with N-face as an upper surface above thebarrier layer 24, may include bonding the p-type GaN-based semiconductorlayer 5 with N-face on the barrier layer 24 directly.

In an embodiment of the present application, for example, the p-typeGaN-based semiconductor layer 5 may be made of one or more of thefollowing materials: p-type AlGaN, p-type GaN, and p-type InGaN.

Step 603: as shown in FIG. 4 a , etching the p-type GaN-basedsemiconductor layer 5 selectively, and reserving only a portion of thep-type GaN-based semiconductor layer corresponding to a gate region.

The gate region in the present application is a region used to prepare agate. It should be understood by those skilled in the art that the gateregion may be defined and determined according to a design and processof relevant devices.

In an embodiment of the present application, the selective etchingprocess for the p-type GaN-based semiconductor layer 5 may be a wetetching process, for example, a wet etching process adopting KOH.

In wet etching, N-face GaN-based materials are easy to be etched, whileGa-face GaN-based materials are not easy to be etched. Therefore, in aprocess of etching the N-face GaN-based material, the etching processmay be easily controlled to avoid damage to the Ga-face GaN-basedmaterial under the N-face GaN-based material.

Since the p-type GaN-based semiconductor layer 5 is a GaN-based materialwith N-face as an upper surface, and the barrier layer is a GaN-basedmaterial with Ga-face as an upper surface, the etching process may beeasily controlled to avoid damage to the barrier layer during theprocess of etching the p-type GaN-based semiconductor layer 5.

The selective etching of the p-type GaN-based semiconductor layer 5 maybe specifically shown in FIGS. 4 b-4 c . First, a mask layer 41 isdeposited on the p-type GaN-based semiconductor layer 5. The mask layer41 may be a dielectric layer such as SiN, SiO₂, or a metal layer such asTi, Ni, etc. Then selective etching is performed, and only the p-typeGaN-based semiconductor layer 5 and the mask layer 41 in the gate regionare retained. The mask layer 41 may play a good role in protecting thep-type GaN-based semiconductor layer 5 during the etching process. Inthis embodiment, the etching may be wet etching, or a combination of wetetching and dry etching to avoid excessive lateral etching reactions inthe gate region during wet etching.

Step 604: as shown in FIG. 5 a , preparing a gate electrode 51, a sourceelectrode 6, and a drain electrode 7.

The gate electrode 51 is prepared on the p-type GaN-based semiconductorlayer 5, the source electrode 6 is prepared in a source region of thebarrier layer 24, and the drain electrode 7 is prepared in a drainregion of the barrier layer 24.

The source region and the drain region in the present application aresimilar to the gate region in the present application, that is, regionsused to prepare a source electrode and a drain electrode. It should beunderstood by those skilled in the art that the regions may be definedand determined according to a design and process of related devices.

It should also be understood that the source electrode 6, the drainelectrode 7, and the electrode material 51 on the p-type GaN-basedsemiconductor layer 5 may be made of a metal material such as a nickelalloy, or may be made of a metal oxide or a semiconductor material. Thepresent application does not limit the specific preparation materials ofthe source electrode 6, the drain electrode 7, and the electrodematerial 51 on the p-type GaN-based semiconductor layer 5.

In an embodiment of the present application, as shown in FIG. 5 b , whenthe electrode material 51 is to be prepared on the p-type GaN-basedsemiconductor material 5 to use as the gate electrode, firstly, apassivation layer 8 may be prepared on an exposed surface of the barrierlayer 24. Then as shown in FIG. 5 b , the electrode material 51 isprepared above the p-type GaN-based semiconductor material 5. Thepassivation layer 8 may be, for example, Al₂O₃, SiO₂, SiN, etc. Thepassivation layer 8 may protect the barrier layer 24 and avoid damage tothe barrier layer 24.

In an embodiment of the present application, as shown in FIG. 6 a , inorder to further improve the performance of the semiconductor structureand further reduce the two-dimensional electron gas density in thechannel layer 23 under the gate region, a groove 4 may be provided inthe gate region of the barrier layer 24 before preparing the p-typeGaN-based semiconductor layer 5. The groove 4 may penetrate the barrierlayer 24 to reach the channel layer 23, or it may stop in the barrierlayer 24. As shown in FIG. 6 b , after the groove 4 is formed, thep-type GaN-based semiconductor layer 5 is prepared above the barrierlayer 24. Then, as shown in FIG. 6 c , the p-type GaN-basedsemiconductor layer 5 is selectively etched, and only the p-typeGaN-based semiconductor layer 5 in the gate region is retained. As shownin FIG. 6 d , the gate electrode 51, the source electrode 6, and thedrain electrode 7 are then prepared.

In an embodiment of the present application, the barrier layer 24 mayadopt a sandwich structure. For example, as shown in FIG. 6 e , thebarrier layer 24 includes a first outer interlayer 241: AlGaN, anintermediate layer 242: GaN, and a second outer interlayer 243: AlGaN.The groove 4 may penetrate the second outer interlayer 243 of thesandwich structure of the barrier layer 24. At this time, theintermediate layer 242 may function as a stop layer in the local etchingprocess for forming the groove 4 to protect the first outer interlayer241 on a surface of the channel layer 23 from damage by the localetching process. However, the present application does not strictlylimit a preparation depth of the groove 4, as long as the p-typeGaN-based semiconductor layer 5 inside the groove 4 may pinch off ann-type conductive layer under the gate to achieve a semiconductorstructure.

As shown in FIG. 5 a , an embodiment of the present application alsoprovides a semiconductor structure. The semiconductor structureincludes: a substrate 1; a channel layer 23 and a barrier layer 24sequentially superimposed on the substrate 1; and a p-type GaN-basedsemiconductor layer 5 formed in a gate region on the barrier layer 24.The barrier layer 24 is made of a GaN-based material, and an uppersurface of the barrier layer 24 is Ga-face. The p-type GaN-basedsemiconductor layer 5 is made of a GaN-based material with N-face as anupper surface.

The substrate 1 may preferably be made of sapphire, diamond, siliconcarbide, silicon, lithium niobate, Silicon on Insulator (SOI), galliumnitride or aluminum nitride.

The channel layer 23 and the barrier layer 24 may be made ofsemiconductor materials that may form a two-dimensional electron gas.For example, taking a GaN-based material as an example, the channellayer 23 may be made of GaN, the barrier layer 24 may be made of AlGaNor AlInGaN, and the channel layer 23 and the barrier layer 24 form aheterostructure to form a two-dimensional electron gas.

In an embodiment, the p-type GaN-based semiconductor layer 5 may be madeof, for example, a multilayer structure or a superlattice structureincluding one or more materials of p-type AlGaN, p-type GaN, and p-typeInGaN.

In a further embodiment of the present application, as shown in FIG. 5 a, in order to improve device performances and meet related technicalrequirements, the semiconductor structure may further include anucleation layer 21 and a buffer layer 22 provided under the channellayer 23. Taking a GaN-based semiconductor structure as an example, inorder to meet technical requirements such as reducing dislocationdensity and defect density, and improving crystal quality, a nucleationlayer 21 prepared above the substrate 1 may be further included. Thenucleation layer 21 may be made of one or more of AlN, AlGaN and GaN. Inaddition, in order to buffer a stress in an epitaxial structure abovethe substrate and prevent the epitaxial structure from cracking, theGaN-based semiconductor structure may further include a buffer layer 22prepared above the nucleation layer 21. The buffer layer 22 may be madeof one or more of GaN, AlGaN, and AlInGaN.

In an embodiment of the present application, as shown in FIG. 5 a , thesemiconductor structure further includes: a source electrode 6 disposedin a source region of the barrier layer 24, a drain electrode 7 disposedin a drain region of the barrier layer 24, and a gate electrode 51disposed on the p-type GaN-based semiconductor layer. The sourceelectrode 6, the drain electrode 7, and the gate electrode 51 may bemade of a conductive metal material such as a nickel alloy, or may bemade of a metal oxide or a semiconductor material. The presentapplication does not limit the specific preparation materials of thesource electrode 6, the drain electrode 7, and the electrode material 51on the p-type GaN-based semiconductor layer 5.

In an embodiment of the present application, as shown in FIG. 6 d , inorder to further improve the performance of the semiconductor structureand further reduce the two-dimensional electron gas density in thechannel layer 23 under the gate region, the semiconductor structure mayfurther include a groove 4 disposed in the gate region of the barrierlayer 24. However, it should be understood that the semiconductorstructure may not include the groove 4, and the p-type GaN-basedsemiconductor layer 5 may be directly prepared in the gate region,considering that the purpose of pinching off an n-type conductive layerunder the gate may be achieved as long as the p-type GaN-basedsemiconductor layer 5 is prepared in the gate region.

In an embodiment of the present application, as shown in FIG. 6 e , whenthe semiconductor structure includes the groove 4, the barrier layer 24may also adopt a sandwich structure. The sandwich structure includes afirst outer interlayer 241 prepared on a surface of the channel layer23, an intermediate layer 242 sandwiched between the first outerinterlayer 241 and a second outer interlayer 243, and the second outerinterlayer 243. It should be understood that the materials of the firstouter interlayer 241, the intermediate layer 242, and the second outerinterlayer 243 may be adjusted according to the material of the channellayer 23. For example, taking a GaN-based material as an example, whenthe channel layer 23 is made of GaN, the first outer interlayer 241 andthe second outer interlayer 243 may be made of AlGaN, and theintermediate layer 242 may be made of GaN. However, the presentapplication does not specifically limit the materials of the first outerinterlayer 241, the intermediate layer 242, and the second outerinterlayer 243.

It should be understood that although this specification is describedaccording to embodiments, not each embodiment only includes oneindependent technical solution. The way of describing is only forclarity purpose, and those skilled in the art should deem thespecification as a whole. The technical solutions in each embodiment mayalso be appropriately combined to form other embodiments that may beunderstood by those skilled in the art.

The series of detailed descriptions listed above are only specificdescriptions of feasible embodiments of the present application. Theyare not intended to limit the protection scope of the presentapplication. Any equivalent embodiments or modifications made within thetechnical spirit of the present application shall be included in theprotection scope of the present application.

What is claimed is:
 1. A semiconductor structure, comprising: asubstrate; a channel layer and a barrier layer sequentially superimposedon the substrate, wherein the channel layer and the barrier layer aremade of GaN-based materials and an upper surface of the barrier layer isGa-face; and a p-type GaN-based semiconductor layer formed in a gateregion of the barrier layer, wherein an upper surface of the p-typeGaN-based semiconductor layer is N-face.
 2. The semiconductor structureaccording to claim 1, further comprising: a gate electrode disposed onthe p-type GaN-based semiconductor layer; a source electrode disposed ina source region of the barrier layer; and a drain electrode disposed ina drain region of the barrier layer.
 3. The semiconductor structureaccording to claim 1, further comprising: a nucleation layer between thechannel layer and the substrate; and a buffer layer between thenucleation layer and the channel layer.
 4. The semiconductor structureaccording to claim 1, wherein the p-type GaN-based semiconductor layercomprises a multilayer structure or a superlattice structure comprisingone or more materials of p-type AlGaN, p-type GaN, and p-type InGaN. 5.The semiconductor structure according to claim 1, further comprising agroove disposed in the gate region of the barrier layer, wherein thegroove penetrates the barrier layer and stops on the channel layer orpartially penetrates the barrier layer and stops in the barrier layer.6. A manufacturing method for a semiconductor structure, comprising:preparing a channel layer and a barrier layer sequentially superimposedon a substrate, wherein the channel layer and the barrier layer are madeof GaN-based materials and an upper surface of the barrier layer isGa-face; and preparing a p-type GaN-based semiconductor layer withN-face as an upper surface above the barrier layer.
 7. The manufacturingmethod for a semiconductor structure according to claim 6, wherein thepreparing a p-type GaN-based semiconductor layer with N-face as an uppersurface above the barrier layer, comprises: preparing a p-type Ga-faceGaN-based material above the barrier layer, and doping a polarityreversal element in the p-type Ga-face GaN-based material to reverse thep-type Ga-face GaN-based material to the p-type GaN-based semiconductorlayer with N-face as an upper surface.
 8. The manufacturing method for asemiconductor structure according to claim 7, wherein the polarityreversal element comprises Mg.
 9. The manufacturing method for asemiconductor structure according to claim 6, wherein the preparing ap-type GaN-based semiconductor layer with N-face as an upper surfaceabove the barrier layer, comprises: preparing a p-type Ga-face GaN-basedmaterial above the barrier layer; and reversing the p-type Ga-faceGaN-based material by a polarity reversal layer to the p-type GaN-basedsemiconductor layer with N-face as an upper surface.
 10. Themanufacturing method for a semiconductor structure according to claim 6,wherein the preparing a p-type GaN-based semiconductor layer with N-faceas an upper surface above the barrier layer, comprises: bonding thep-type GaN-based semiconductor layer with N-face as an upper surface tothe barrier layer directly.
 11. The manufacturing method for asemiconductor structure according to claim 6, further comprising:etching the p-type GaN-based semiconductor layer selectively, andreserving only a portion of the p-type GaN-based semiconductor layercorresponding to a gate region.
 12. The manufacturing method for asemiconductor structure according to claim 6, further comprising:preparing a gate electrode on the p-type GaN-based semiconductor layer,preparing a source electrode in a source region of the barrier layer,and preparing a drain electrode in a drain region of the barrier layer.13. The manufacturing method for a semiconductor structure according toclaim 6, further comprising: forming a nucleation layer and a bufferlayer on the substrate sequentially before forming the channel layer.14. The manufacturing method for a semiconductor structure according toclaim 6, before the preparing a p-type GaN-based semiconductor layerwith an N-face as an upper surface above the barrier layer, furthercomprising: preparing a groove in a gate region of the barrier layer,wherein the groove penetrates the barrier layer and stops on the channellayer or partially penetrates the barrier layer and stops in the barrierlayer.